<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .container {
            width: 100%;
            background-color: #f0f;
            padding-top: 75%;
            position: relative;
        }

        .item {
            position: absolute;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            background-color: #000;
        }
    </style>
</head>

<body>
    <div class="container">
        <div class="item"></div>
    </div>
</body>

</html>